Browsing by Issue Date, starting with "2015-03-02"

Now showing 1 - 20 of 22311

Manipulation of nanoscale V-pits to optimize internal quantum efficiency of InGaN multiple quantum wells
(2015-03-02)
Chang, Chiao-Yun
;
Li, Heng
;
Shih, Yang-Ta
;
Lu, Tien-Chang
;
光電工程學系
We systematically investigated the influence of nanoscale V-pits on the internal quantum efficiency (IQE) of InGaN multiple quantum wells (MQWs) by adjusting the underlying superlattices (SLS). The analysis indicated that high barrier energy of sidewall MQWs on V-pits and long diffusion distance between the threading dislocation (TD) center and V-pit boundary were crucial to effectively passivate the non-radiative centers of TDs. For a larger V-pit, the thicker sidewall MQW on V-pit would decrease the barrier energy. On the contrary, a shorter distance between the TD center and V-pit boundary would be observed in a smaller V-pit, which could increase the carrier capturing capability of TDs. An optimized V-pit size of approximately 200-250 nm in our experiment could be concluded for MQWs with 15 pairs SLS, which exhibited an IQE value of 70%. (C) 2015 AIP Publishing LLC.
Event trigger and management system for providing automatic repeat requests by single timer and method thereof
(2015-03-03)
Hsiao Hsu-Feng
;
Tseng Kuan-Ju
;
Lee Chung-Nan
An event trigger and management system for providing automatic repeat requests (ARQs) by a single timer and a method thereof are provided. Various type timers for providing an ARQ are integrated into a single timer. Through a data structure of a timer node of automatic repeat requests time series, the automatic repeat request time series can be managed only by a single timer. Therefore, the efficiency of controlling and managing a timer associated with Worldwide Interoperability for Microwave Access (WiMAX) may be achieved.
Effect of the Polymer Concentration on the Rayleigh-Instability-Type Transformation in Polymer Thin Films Coated in the Nanopores of Anodic Aluminum Oxide Templates
(2015-03-03)
Tsai, Chia-Chan
;
Chen, Jiun-Tai
;
應用化學系
;
Department of Applied Chemistry
We study the Rayleigh-instability-type transformation of polystyrene (PS) thin films coated in the nanopores of anodic aluminum oxide (AAO) templates. The PS thin films are fabricated using a solution-wetting method, in which the wall thicknesses are controlled by the concentrations of the polymer solutions and the diameters of the nanopores. By thermal annealing, the surfaces of the thin films undulate and the morphologies transform from nanotubes to Rayleigh-instability-induced nanostructures (short nanorods) and long nanorods. To understand the mechanism of the morphology transformation further, we construct the morphology diagrams by annealing the PS thin films at different temperatures and times. We observe that the morphology diagrams of the PS thin films prepared by different concentrations are similar, indicating that the transformation kinetics are not affected by the film thicknesses. The values of the undulation wavelengths, however, are controlled by the film thicknesses and the diameters of the nanopores.
Thin film transistor with UV light absorber layer
(2015-03-03)
Shieh Han-Ping D.
;
Liu Po-Tsun
;
Tsai Yun-Chu
;
Tsai Min-Yen
;
Teng Li-Feng
A thin film transistor comprises a transparent substrate, a gate is disposed on the transparent substrate, a gate insulator is disposed on the gate and the transparent substrate, an active layer is disposed on the gate insulator, an electrode layer is electrically connected the active layer and the portion of the active layer is exposed, and an ultraviolet light absorbing layer is disposed on the electrode layer. By using the advantage of the ultraviolet light absorbing layer with the range of visible light transmittance and with the component protection, preventing the optical characteristics of the thin film transistor from the outside moisture is achieved, and by adjusting the parameters in the thin film deposition process to change its conductivity.
Oxidative Stress Activates Endothelial Innate Immunity via Sterol Regulatory Element Binding Protein 2 (SREBP2) Transactivation of MicroRNA-92a
(2015-03-03)
Chen, Zhen
;
Wen, Liang
;
Martin, Marcy
;
Hsu, Chien-Yi
;
Fang, Longhou
Background-Oxidative stress activates endothelial innate immunity and disrupts endothelial functions, including endothelial nitric oxide synthase-derived nitric oxide bioavailability. Here, we postulated that oxidative stress induces sterol regulatory element-binding protein 2 (SREBP2) and microRNA-92a (miR-92a), which in turn activate endothelial innate immune response, leading to dysfunctional endothelium. Methods and Results-Using cultured endothelial cells challenged by diverse oxidative stresses, hypercholesterolemic zebrafish, and angiotensin II-infused or aged mice, we demonstrated that SREBP2 transactivation of microRNA-92a (miR-92a) is oxidative stress inducible. The SREBP2-induced miR-92a targets key molecules in endothelial homeostasis, including sirtuin 1, Kruppel-like factor 2, and Kruppel-like factor 4, leading to NOD-like receptor family pyrin domain-containing 3 inflammasome activation and endothelial nitric oxide synthase inhibition. In endothelial cell-specific SREBP2 transgenic mice, locked nucleic acid-modified antisense miR-92a attenuates inflammasome, improves vasodilation, and ameliorates angiotensin II-induced and aging-related atherogenesis. In patients with coronary artery disease, the level of circulating miR-92a is inversely correlated with endothelial cell-dependent, flow-mediated vasodilation and is positively correlated with serum level of interleukin-1 beta. Conclusions-Our findings suggest that SREBP2-miR-92a-inflammasome exacerbates endothelial dysfunction during oxidative stress. Identification of this mechanism may help in the diagnosis or treatment of disorders associated with oxidative stress, innate immune activation, and endothelial dysfunction.
Arithmetic module, device and system
(2015-03-03)
Liu Chih-Wei
;
Chang Kuo-Chiang
;
Ou Shih-Hao
;
Chen Yu-Wen
An arithmetic module is provided, including a first adder, a first shifter coupled to the first adder, a multiplier coupled to the first shifter for receiving an external coefficient signal, a digit alignment unit coupled to the multiplier, a second adder coupled to the digit alignment unit, and a second shifter coupled to the second adder. The arithmetic module reduces the overall computation time effectively, as compared with a scalar processor, by employing a serial data connection design, and also significantly reduces power consumption of the digital signal processor by requiring fewer input and output ends than those of a multi-issue processor.
Electron-electron interaction effect on longitudinal and Hall transport in thin and thick Ag-x(SnO2)(1-x) granular metals
(2015-03-03)
Wu, Ya-Nan
;
Wei, Yan-Fang
;
Li, Zhi-Qing
;
Lin, Juhn-Jong
;
電子物理學系
We study the temperature behaviors of the Hall coefficient, R-H, and longitudinal conductivity, sigma, of two series of Ag-x(SnO2)(1-x) (x being the Ag volume fraction) granular films lying in the metallic regime. The first (second) series of films are similar to 500 (similar to 9) nm thick and constitute a three-(two-) dimensional granular array. In the high-x regime with g(T) >> g(T)(c) (g(T) being the dimensionless intergrain tunneling conductance, and g(T)(c) being the critical tunneling conductance at the percolation threshold), we observe a R-H alpha ln T law from similar to 6 to 300K. This ln T behavior is independent of array dimensionality. We also observe a sigma alpha ln T law in the temperature range similar to 20-100 K. Below similar to 10 K, the temperature behavior of sigma changes to a root T dependence in thick films, while it changes to a different ln T dependence in thin films. The overall R-H and sigma characteristics can be explained by the electron-electron interaction (EEI) effects in the presence of granularity. As x is reduced and approaches the percolation threshold, we found that the ln T dependences of R-H and sigma still hold for a wide temperature range. We propose an explanation for the long-standing puzzle of the sigma alpha ln T dependence, which has previously been frequently observed in composite systems near the quantum percolation threshold, as arising from the same EEI effect considered in the recent theory of granular metals.
Use of Ultrafast Time-Resolved Spectroscopy to Demonstrate the Effect of Annealing on the Performance of P3HT:PCBM Solar Cells
(2015-03-04)
Wang, Yu-Ting
;
Chen, Mei-Hsin
;
Lin, Chao-Ting
;
Fang, Jian-Jhih
;
Chang, Che-Jui
The organic solar cells of heterojunction system, ITO/PEDOT:PSS/P3HT:PCBM/Al, with a thermal annealing after deposition of Al exhibit better performance than those with an annealing process before deposition of Al. In this study, ultrafast time-resolved spectroscopy is employed to reveal the underlying mechanism of annealing effects on the performance of P3HT:PCBM solar cell devices. The analyses of all decomposed relaxation processes show that the postannealed devices exhibit an increase in charge transfer, in the number of separated polarons and a reduction in the amount of recombination between excited carriers. Moreover, the longer lifetime for the excited carriers in postannealed devices indicates it is more likely to be dissociated into photocarriers and result in a larger value for photocurrent, which demonstrates the physical mechanism for increased device performance.
The benefits of a challenge: student motivation and flow experience in tablet-PC-game-based learning
(2015-03-04)
Hung, Cheng-Yu
;
Sun, Jerry Chih-Yuan
;
Yu, Pao-Ta
;
教育研究所
;
Institute of Education
Advances in technology have led to continuous innovation in teaching and learning methods. For instance, the use of tablet PCs (TPCs) in classroom instruction has been shown to be effective in attracting and motivating students\' interest and increasing their desire to participate in learning activities. In this paper, we used a TPCs game - an iPad app called Motion Math: Hungry Fish - to help young students learn to theoretically understand and practically implement the mathematical concepts of addition and subtraction. Based on findings from a pilot study, we categorized the game\'s 18 levels of difficulty into "challenging" (experimental group) and "matching" (control group) games. We aimed to investigate whether challenging games were more able than matching games to improve the students\' motivation, flow experience, self-efficacy for technology, self-efficacy for science, feelings about the TPC game, and satisfaction with the learning approach. The findings showed that the students in the experimental group achieved better flow experience, learning performance, and satisfaction.
A powerful test for two-sided multiple independent characteristics supplier selection problem
(2015-03-04)
Wu, C. H.
;
Pearn, W. L.
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Chuang, C. C.
;
工業工程與管理學系
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Department of Industrial Engineering and Management
In this article, we consider the supplier selection problem for two-sided processes with multiple independent characteristics. We review the existing division method and develop a new exact approach called the subtraction method. For practical applications, a two-phase selection procedure is established based on the subtraction method. The decision powers of two methods are compared. We show that the subtraction method we proposed is indeed more powerful than the existing division method. Several figures are presented to display the required sample sizes with various powers and various values of (C-pk1(T), C-pk2(T)). For the convenience of practitioners, the required sample sizes for the two methods with various powers and various values of (C-pk1(T), C-pk2(T))) are also tabulated.
Detecting Misspecified Multilevel Structural Equation Models with Common Fit Indices: AMonte Carlo Study
(2015-03-04)
Hsu, Hsien-Yuan
;
Kwok, Oi-man
;
Lin, Jr Huang
;
Acosta, Sandra
;
教育研究所
This study investigated the sensitivity of common fit indices (i.e., RMSEA, CFI, TLI, SRMR-W, and SRMR-B) for detecting misspecified multilevel SEMs. The design factors for the Monte Carlo study were numbers of groups in between-group models (100, 150, and 300), group size (10, 20, 30, and 60), intra-class correlation (low, medium, and high), and the types of model misspecification (Simple and Complex). The simulation results showed that CFI, TLI, and RMSEA could only identify the misspecification in the within-group model. Additionally, CFI, TLI, and RMSEA were more sensitive to misspecification in pattern coefficients while SRMR-W was more sensitive to misspecification in factor covariance. Moreover, TLI outperformed both CFI and RMSEA in terms of the hit rates of detecting the within-group misspecification in factor covariance. On the other hand, SRMR-B was the only fit index sensitive to misspecification in the between-group model and more sensitive to misspecification in factor covariance than misspecification in pattern coefficients. Finally, we found that the influence of ICC on the performance of targeted fit indices was trivial.
Double-finger-gate controlled spin-resolved resonant quantum transport in the presence of a Rashba-Zeeman gap
(2015-03-04)
Tang, Chi-Shung
;
Tseng, Shu-Ting
;
Gudmundsson, Vidar
;
Cheng, Shun-Jen
;
電子物理學系
We investigate double finger gate (DFG) controlled spin-resolved resonant transport properties in an n-type quantum channel with a Rashba-Zeeman (RZ) subband energy gap. By appropriately tuning the DFG in the strong Rashba coupling regime, resonant state structures in conductance can be found that are sensitive to the length of the DFG system. Furthermore, a hole-like bound state feature below the RZ gap and an electron-like quasi-bound state feature at the threshold of the upper spin branch can be found that is insensitive to the length of the DFG system.
High-efficiency parallel-plate wet scrubber (PPWS) for soluble gas removal
(2015-03-04)
Chien, Chih-Liang
;
Tsai, Chuen-Jinn
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Sheu, Shiang-Ru
;
Cheng, Yu-Hsiang
;
Stank, Alexander Mihailovich
A parallel-plate wet scrubber (PPWS) was designed and tested to control low-concentration soluble acid gases using a multi-parallel-plate module (MPPM) to replace typical tower packings. The parallel plates in the MPPM were made of polypropylene coated with nano-TiO2 particles to enhance hydrophilicity for scrubbing liquid to form uniform liquid film. The gap between the plates was maintained at 3 mm, providing channels through which soluble gas pollutants in the upward gas stream were absorbed by the downward scrubbing liquid film on the surfaces. The removal efficiency was tested using HCl, HNO3, and CH3COOH of 0.02-2 ppmv at different retention times and liquid-to-gas ratios. Results show that when the retention time was 0.1, 0.3 and 0.5 s, the removal efficiency of the present scrubber for HCI, HNO3, and CH3COOH in low concentration was greater than 91%, 95%, and 98%, respectively. The MPPM significantly enhances the removal efficiency of the present scrubber, especially in low inlet concentration range (0.02-1 ppmv), which was greater than 99% for HCl and HNO3 and 98% for CH3COOH at the liquid-to-gas ratio of 18.5 L/m(3), the retention time of 0.5 s, and the pressure drop of 0.2 cm H2O. The experimental removal efficiencies of the MPPM are in good agreement with theoretical predictions. It is expected that the present PPWS can be scaled up as an efficient control device with low pressure drop for low-concentration soluble acid and basic gases. (C) 2015 Elsevier B.V. All rights reserved.
SINGLE CRYSTAL COPPER, MANUFACTURING METHOD THEREOF AND SUBSTRATE COMPRISING THE SAME
(2015-03-05)
CHEN Chih
;
TU King-Ning
;
LU Chia-Ling
The present invention relates to a single crystal copper having [100] orientation and a volume of 0.1˜4.0×106 μm3. The present invention further provides a manufacturing method for the single crystal copper and a substrate comprising the same.
Single-input multiple-output visible light optical wireless communications supporting quality of service
(2015-03-05)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
Visible light optical wireless communication supporting single-input multiple-output quality of service (QoS) by using an indoor light-emitting diode, a mobile-phone camera and a photodetector is proposed and demonstrated for the first time. The proposed system can support two fixed-rate QoS transmissions for two different applications. By employing the rolling shutter effect of the mobile-phone camera, the data rate of the first data link can be greatly enhanced. The experimental result shows that the proposed system can support the first data link operated at 300 bit/s by using a mobile-phone camera and the second data link at 38.4 kbit/s by using a photodetector.
SECRET COMMUNICATION METHOD WITH SELF-AUTHENTICATION CAPABILITY
(2015-03-05)
LEE CHE-WEI
;
TSAI WEN-HSIANG
A secret communication method with a self-authentication capability is provided, which comprises steps of dividing a secret message into a plurality of secret segments; converting each of the secret segments into (k+1) shares, wherein k is a positive integer; embedding the shares into a media carrier; selecting every k shares among the (k+1) ones to compute (k+1) copies in value; and checking if the (k+1) copies in value are the same. If the (k+1) copies in value are the same, then the secret message is shown. Otherwise, at least one mark will be utilized to replace the secret message while the part of the secret message which is not falsified can still be correctly shown. By employing the method, the integrity and fidelity of the hidden secret message can thus be verified, thereby achieving a new covert communication process performing both information hiding and self-authentication capability.
Hybrid Dendrimer/Semiconductor Nanostructures with Efficient Energy Transfer via Optical Waveguiding
(2015-03-05)
Lin, T. N.
;
Huang, J. C.
;
Shen, J. L.
;
Chu, C. M.
;
Yeh, J. M.
In this study, we demonstrated a nonradiative energy transfer between InGaN quantum wells (QWs) and polyamidoamine (PAMAM) dendrimers through optical waveguiding by detecting a reduction in the photoluminescence lifetime. The maximum energy transfer efficiency of this system is similar to 72%, which is promising for sensor applications. The energy transfer efficiency depends on the distance between the InGaN QWs and PAMAM dendrimers by a factor of 1/d(2), revealing layer-to-layer dipole interactions. Upon increasing the generation of PAMAM dendrimers, the transfer energy efficiency increases exponentially, which can be explained by the increased surface coverage for the higher generation.
GRAPHITE OXIDE AND GRAPHENE PREPARATION METHOD
(2015-03-05)
WEI Kung-Hwa
;
DANG Van Thanh
A graphite oxide and/or graphene preparation method includes providing a plasma electrolytic apparatus, wherein an electrolyte is provided and a graphite electrode is configured as a cathode of the plasma electrolytic apparatus; and providing a cathodic current so as to initiate a plasma electrolytic process at the graphite electrode to obtain graphite oxide and/or graphene. The graphite oxide and/or graphene can be synthesized through plasma electrolytic processing at relatively low temperature under atmospheric pressure within a very short period of time, without the need for concentrated acids or strong oxidizing agents. The present invention may prepare graphite oxide and/or graphene with plasma electrolytic process directly from graphite, without requiring any prior purification or pretreatment. This plasma electrolytic process of the present invention is quite promising and provided with advantages such as low cost, simple setup, high efficiency, and environmental friendliness.
Efficiency droop behavior improvement through barrier thickness modification for GaN-on-silicon light-emitting diodes
(2015-03-05)
Tzou, An-Jye
;
Lin, Bing-Cheng
;
Lee, Chia-Yu
;
Lin, Da-Wei
;
Liao, Yu-Kuang
Crack-free GaN-based light-emitting diodes (LEDs) were grown on 150-mm-diameter Si substrates by using low-pressure metal-organic chemical vapor deposition. The relationship between the LED devices and the thickness of quantum barriers (QBs) was investigated. The crystal quality and surface cracking of GaN-on-Si were greatly improved by an AlxGa1-xN buffer layer composed of graded Al. The threading dislocation density of the GaN-on-Si LEDs was reduced to < 7 x 10(8) cm(-2), yielding LEDs with high internal quantum efficiency. Simulation results indicated that reducing the QB thickness improved the carrier injection rate and distribution, thereby improving the droop behavior of the LEDs. LEDs featuring 6-nm-thick QBs exhibited the lowest droop behavior. However, the experimental results showed an unanticipated phenomenon, namely that the peak external quantum efficiency (EQE) and light output power (LOP) gradually decreased with a decreasing QB thickness. In other words, the GaN-on-Si LEDs with 8-nm-thick QBs exhibited low droop behavior and yielded a good peak EQE and LOP, achieving a 22.9% efficiency droop and 54.6% EQE. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Direct Observation of the Solvent Effects on the Low-Lying ne and pi pi* Excited Triplet States of Acetophenone Derivatives in Thermal Equilibrium
(2015-03-05)
Narra, Sudhakar
;
Shigeto, Shinsuke
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
Low-lying excited triplet states of aromatic carbonyl compounds exhibit diverse photophysical and photochemical properties of fundamental importance. Despite tremendous effort in studying those triplet states, the effects of substituents and solvents on the energetics of the triplet manifold and on photoreactivity remain to be fully understood. We have recently studied the ordering of the low-lying n pi* and pi pi* excited triplet states and its substituent dependence in acetophenone derivatives using nanosecond time-resolved near-IR (NIR) spectroscopy. Here we address the other important issue, the solvent effects, by directly observing the electronic bands in the NIR that originate from the lowest n pi* and pi pi* states of acetophenone derivatives in four solvents of different polarity (n-heptane, benzene, acetonitrile, and methanol). The two transient NIR bands decay synchronously in all the solvents, indicating that the lowest n pi* and pi pi* states are in thermal equilibrium irrespective of the solvent polarity studied here. We found that the pi pi* band increases in intensity relative to the n pi* band as solvent polarity increases. These results are compared with the photoreduction rate constant for the acetophenone derivatives in the solvents to which 2-propanol was added as a hydrogen-atom donor. Based on the present findings, we present a comprehensive, solvent- and substituent-dependent energy level diagram of the low-lying n pi* and pi pi* excited triplet states.